Ken Livingstone and Boris Johnson at loggerheads over London mayoral position Credit: ITV News

A spokesman for Boris Johnson has said: "Boris Johnson has repeatedly made clear he pays all taxes in full. Ken Livingstone knows this because he has been personally told by Boris Johnson during a private conversation at a business hustings just two weeks ago.

“Mr Livingstone repeated these false claims today, knowing full well they are not true, in a desperate attempt to avoid answering serious questions over his own tax affairs".

Boris Johnson said: "Of course the real point is not about my tax arrangements. It is about the hypocrisy of a man who for years has railed against those who use special arrangements to reduce their tax and who has then been caught – bang to rights – doing the very same thing himself."

Boris Johnson and Ken Livingstone were involved in a furious row in the lift after the London mayoral debate at LBC Radio. Sources say Johnson and Livingstone were "nose to nose" and Johnson 's face was "red with rage".